1. Field of the Invention
This invention relates to calibrating Instruments and, more particularly, to a method and apparatus for on-site calibration of a machine condition monitoring vibration measuring instrument (MCM instrument).
2. Background Art
Owners of MCM instrument conventionally return equipment back to the original equipment manufacturer's (OEM) lab or to a third party calibration lab by one of the many conventional shipping companies (e.g. UPS, FedEx, etc.) to be calibrated to NIST (National Institute of Standards and Technology) standards. This method entails shipping expense, possible shipping damage of the equipment, shipping delays, and backlog delays at the lab, as well as requiring the handling and packaging of the equipment for shipment at both ends. This conventional method is shown in FIG. 11, where experience indicates a 2–5 day delay in shipping at both ends, dependent on distance and type of shipping method used (i.e. ground, next-day air, etc.), plus a backlog delay at the testing lab of 5–14 days.
After receipt of this MCM instrument, the lab performs the calibration using such testing equipment as a Digital Voltmeter (DVM), Signal Generator, Frequency Counter and a shaker table for checking vibration transducers or vibration pickups. This test equipment is very large, not mobile and very expensive. The labs use calibration procedures, which include (a) written instructions on how to connect test cables between the MCM instrument being calibrated and test equipment, and how to connect test cables between the MCM instrument and test equipment; and (b) procedures of data collection of the MCM instrument.
Different calibration methods are used for different makes and models of instrumentation. Data Collection is taken by comparing various amplitude and frequency standards with test equipment readings from the MCM Instrument being calibrated. Amplitude and frequency readings from the MCM instrument is manually written down into a form. If the reading from the MCM instrument is within the Standards, a Calibration Certificate is provided to the owner of the MCM instrument.
After completion of the calibration procedure, the lab returns MCM instrument to the owner by the same shipping method as previous, entailing additional shipping expense, potential shipping damage to the equipment, and added delay, as shown in FIG. 11.
The turnaround time required for this method of calibration the MCM instrument is on the order of 9–24 days total, during which time period, the MCM instrument is unavailable for usage.
It would be desirable to provide a method for calibrating MCM instruments that reduce the time required for calibration, and reduce shipping expense and equipment damage.